Method for support of scalability with adaptive picture resolution

ABSTRACT

A method and apparatus for decoding multiple semantically independent picture parts into a single video picture includes decoding unique picture order count values for each coded picture, coded slice, or coded tile in a coded video sequence, with multiple decoded pictures, cycles, and tiles belonging to a same access unit representing a frame of the video. A value representing the amount of pictures, cycles, or tiles, is then assigned to each access unit for assigning sequential access unit count values to the access units. As a result, each access unit, which represents multiple pictures, slices, or tiles to be combined into a single frame, is decoded for display processing.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation application of U.S. patent application Ser. No.16/905,475, filed Jun. 18, 2020, in the U.S. Patent and TrademarkOffice, which application claims priority under 35 U.S.C. § 119 fromU.S. Provisional Application No. 62/864,475 filed on Jun. 20, 2019 inthe U.S. Patent & Trademark Office, the disclosure of which isincorporated herein by reference in its entirety.

FIELD

The disclosed subject matter relates to video coding and decoding, andmore specifically, to the signaling of picture, or parts of a picture,size that may change from picture to picture or picture part to picturepart, to support temporal or spatial scalability.

BACKGROUND

Video coding and decoding using inter-picture prediction with motioncompensation has been known for decades. Uncompressed digital video canconsist of a series of pictures, each picture having a spatial dimensionof, for example, 1920×1080 luminance samples and associated chrominancesamples. The series of pictures can have a fixed or variable picturerate (informally also known as frame rate), of, for example 60 picturesper second or 60 Hz. Uncompressed video has significant bitraterequirements. For example, 1080p60 4:2:0 video at 8 bit per sample(1920×1080 luminance sample resolution at 60 Hz frame rate) requiresclose to 1.5 Gbit/s bandwidth. An hour of such video requires more than600 GByte of storage space.

One purpose of video coding and decoding can be the reduction ofredundancy in the input video signal, through compression. Compressioncan help reducing aforementioned bandwidth or storage spacerequirements, in some cases by two orders of magnitude or more. Bothlossless and lossy compression, as well as a combination thereof can beemployed. Lossless compression refers to techniques where an exact copyof the original signal can be reconstructed from the compressed originalsignal. When using lossy compression, the reconstructed signal may notbe identical to the original signal, but the distortion between originaland reconstructed signal is small enough to make the reconstructedsignal useful for the intended application. In the case of video, lossycompression is widely employed. The amount of distortion tolerateddepends on the application; for example, users of certain consumerstreaming applications may tolerate higher distortion than users oftelevision contribution applications. The compression ratio achievablecan reflect that: higher allowable/tolerable distortion can yield highercompression ratios.

A video encoder and decoder can utilize techniques from several broadcategories, including, for example, motion compensation, transform,quantization, and entropy coding, some of which will be introducedbelow.

Historically, video encoders and decoders tended to operate on a givenpicture size that was, in most cases, defined and stayed constant for acoded video sequence (CVS), Group of Pictures (GOP), or a similarmulti-picture timeframe. For example, in MPEG-2, system designs areknown to change the horizontal resolution (and, thereby, the picturesize) dependent on factors such as activity of the scene, but only at Ipictures, hence typically for a GOP. The resampling of referencepictures for use of different resolutions within a CVS is known, forexample, from ITU-T Rec. H.263 Annex P. However, here the picture sizedoes not change, only the reference pictures are being resampled,resulting potentially in only parts of the picture canvas being used (incase of downsampling), or only parts of the scene being captured (incase of upsampling). Further, H.263 Annex Q allows the resampling of anindividual macroblock by a factor of two (in each dimension), upward ordownward. Again, the picture size remains the same. The size of amacroblock is fixed in H.263, and therefore does not need to besignaled.

Changes of picture size in predicted pictures became more mainstream inmodern video coding. For example, VP9 allows reference pictureresampling and change of resolution for a whole picture. Similarly,certain proposals made towards VVC (including, for example, Hendry, et.al, “On adaptive resolution change (ARC) for VVC”, Joint Video Teamdocument JVET-M0135-v1, Jan. 9-19, 2019, incorporated herein in itsentirety) allow for resampling of whole reference pictures todifferent—higher or lower—resolutions. Specifically, different candidateresolutions are suggested to be coded in the sequence parameter set andreferred to by per-picture syntax elements in the picture parameter set.

According to an aspect of the disclosure, a method for video decodingincludes decoding a first of at least one of a coded picture, a codedslice, and a coded tile with a first value of a picture order countincluded in a coded video sequence; and decoding a second of at leastone of a coded picture, a coded slice, and a coded tile with a secondvalue of the picture order count included in the coded video sequence.The first and the second of the at least one of the coded picture, thecoded slice, or the coded tile belong to a same access unit, the firstand the second values of the picture order count are different, and anaccess unit corresponds to a time instance.

According to an aspect of the disclosure, a device for video decodingincluding at least one memory configured to store program code; and atleast one processor configured to read the program code and operate asinstructed by the program code, the program code including: a firstdecoding code configured to cause the at least one processor to decode afirst of at least one of a coded picture, a coded slice, and a codedtile with a first value of a picture order count included in a codedvideo sequence; and a second decoding code configured to cause the atleast one processor to decode a second of at least one of a codedpicture, coded slice, and coded tile with a second value of the pictureorder count included in the coded video sequence; wherein the first andthe second of the at least one coded picture, coded slice, or coded tilebelong to a same access unit, the first and the second values of thepicture order count are different, and an access unit corresponds to atime instance.

According to an aspect of the disclosure, a non-transitory computerreadable medium storing instructions, the instructions including one ormore instructions that, when executed by one or more processors of adevice, cause one or more processors to: decode a first of at least oneof a coded picture, coded slice, and coded tile with a first value of apicture order count included in a coded video sequence; and decoding asecond of at least one of a coded picture, coded slice, and coded tilewith a second value of the picture order count included in the codedvideo sequence; wherein the first and the second coded picture, codedslice, or coded tile belong to a same access unit, the first and thesecond values of the picture order count are different, and an accessunit corresponds to a time instance.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, the nature, and various advantages of the disclosedsubject matter will be more apparent from the following detaileddescription and the accompanying drawings in which:

FIG. 1 is a schematic illustration of a simplified block diagram of acommunication system in accordance with an embodiment.

FIG. 2 is a schematic illustration of a simplified block diagram of acommunication system in accordance with an embodiment.

FIG. 3 is a schematic illustration of a simplified block diagram of adecoder in accordance with an embodiment.

FIG. 4 is a schematic illustration of a simplified block diagram of anencoder in accordance with an embodiment.

FIG. 5A is a schematic illustration of prior art options for signalingARC parameters, as indicated.

FIG. 5B is a schematic illustration of options for signaling ARCparameters in accordance with an embodiment, as indicated.

FIG. 6 is a syntax table in accordance with an embodiment.

FIG. 7 is a schematic illustration of a computer system in accordancewith an embodiment.

FIG. 8 is a prediction structure for scalability with adaptiveresolution change.

FIG. 9 is a syntax table in accordance with an embodiment.

FIG. 10 is a schematic illustration of a simplified block diagram ofparsing and decoding picture order count (POC) cycle per access unit andaccess unit count value.

DETAILED DESCRIPTION

Recently, compressed domain aggregation or extraction of multiplesemantically independent picture parts into a single video picture hasgained some attention. In particular, in the context of, for example,360 coding or certain surveillance applications, multiple semanticallyindependent source pictures (for examples the six cube surface of acube-projected 360 scene, or individual camera inputs in case of amulti-camera surveillance setup) may require separate adaptiveresolution settings to cope with different per-scene activity at a givenpoint in time. In other words, encoders, at a given point in time, maychoose to use different resampling factors for different semanticallyindependent pictures that make up the whole 360 or surveillance scene.When combined into a single picture, that, in turn, requires thatreference picture resampling is performed, and adaptive resolutioncoding signaling is available, for parts of a coded picture.

FIG. 1 illustrates a simplified block diagram of a communication system(100) according to an embodiment of the present disclosure. The system(100) may include at least two terminals (110-120) interconnected via anetwork (150). For unidirectional transmission of data, a first terminal(110) may code video data at a local location for transmission to theother terminal (120) via the network (150). The second terminal (120)may receive the coded video data of the other terminal from the network(150), decode the coded data and display the recovered video data.Unidirectional data transmission may be common in media servingapplications and the like.

FIG. 1 illustrates a second pair of terminals (130, 140) provided tosupport bidirectional transmission of coded video that may occur, forexample, during videoconferencing. For bidirectional transmission ofdata, each terminal (130, 140) may code video data captured at a locallocation for transmission to the other terminal via the network (150).Each terminal (130, 140) also may receive the coded video datatransmitted by the other terminal, may decode the coded data and maydisplay the recovered video data at a local display device.

In FIG. 1 , the terminals (110-140) may be illustrated as servers,personal computers and smart phones but the principles of the presentdisclosure may be not so limited. Embodiments of the present disclosurefind application with laptop computers, tablet computers, media playersand/or dedicated video conferencing equipment. The network (150)represents any number of networks that convey coded video data among theterminals (110-140), including for example wireline and/or wirelesscommunication networks. The communication network (150) may exchangedata in circuit-switched and/or packet-switched channels. Representativenetworks include telecommunications networks, local area networks, widearea networks and/or the Internet. For the purposes of the presentdiscussion, the architecture and topology of the network (150) may beimmaterial to the operation of the present disclosure unless explainedherein below.

FIG. 2 illustrates, as an example for an application of the disclosedsubject matter, the placement of a video encoder and decoder in astreaming environment. The disclosed subject matter can be equallyapplicable to other video enabled applications, including, for example,video conferencing, digital TV, storing of compressed video on digitalmedia including CD, DVD, memory stick and the like, and so on.

A streaming system may include a capture subsystem (213), that caninclude a video source (201), for example a digital camera, creating afor example uncompressed video sample stream (202). That sample stream(202), depicted as a bold line to emphasize a high data volume whencompared to encoded video bitstreams, can be processed by an encoder(203) coupled to the camera (201). The encoder (203) can includehardware, software, or a combination thereof to enable or implementaspects of the disclosed subject matter as described in more detailbelow. The encoded video bitstream (204), depicted as a thin line toemphasize the lower data volume when compared to the sample stream, canbe stored on a streaming server (205) for future use. One or morestreaming clients (206, 208) can access the streaming server (205) toretrieve copies (207, 209) of the encoded video bitstream (204). Aclient (206) can include a video decoder (210) which decodes theincoming copy of the encoded video bitstream (207) and creates anoutgoing video sample stream (211) that can be rendered on a display(212) or other rendering device (not depicted). In some streamingsystems, the video bitstreams (204, 207, 209) can be encoded accordingto certain video coding/compression standards. Examples of thosestandards include ITU-T Recommendation H.265. Under development is avideo coding standard informally known as Versatile Video Coding or VVC.The disclosed subject matter may be used in the context of VVC.

FIG. 3 is a functional block diagram of a video decoder (210) accordingto an embodiment of the present disclosure.

A receiver (310) may receive one or more codec video sequences to bedecoded by the decoder (210). In some embodiments, the receiver (301)may receive one coded video sequence at a time, where the decoding ofeach coded video sequence is independent from other coded videosequences. The coded video sequence may be received from a channel(312), which may be a hardware/software link to a storage device whichstores the encoded video data. The receiver (310) may receive theencoded video data with other data, for example, coded audio data and/orancillary data streams, that may be forwarded to their respective usingentities (not depicted). The receiver (310) may separate the coded videosequence from the other data. To combat network jitter, a buffer memory(315) may be coupled in between receiver (310) and entropydecoder/parser (320) (“parser” henceforth). When receiver (310) isreceiving data from a store/forward device of sufficient bandwidth andcontrollability, or from an isosychronous network, the buffer (315) maynot be needed, or can be small. For use on best effort packet networkssuch as the Internet, the buffer (315) may be required, can becomparatively large and can advantageously of adaptive size.

The video decoder (210) may include a parser (320) to reconstructsymbols (321) from the entropy coded video sequence. Categories of thosesymbols include information used to manage operation of the decoder(210), and potentially information to control a rendering device such asa display (212) that is not an integral part of the decoder but can becoupled to it, as was shown in FIG. 2 . The control information for therendering device(s) may be in the form of Supplementary EnhancementInformation (SEI messages) or Video Usability Information (VUI)parameter set fragments (not depicted). The parser (320) mayparse/entropy-decode the coded video sequence received. The coding ofthe coded video sequence can be in accordance with a video codingtechnology or standard, and can follow principles well known to a personskilled in the art, including variable length coding, Huffman coding,arithmetic coding with or without context sensitivity, and so forth. Theparser (320) may extract from the coded video sequence, a set ofsubgroup parameters for at least one of the subgroups of pixels in thevideo decoder, based upon at least one parameters corresponding to thegroup. Subgroups can include Groups of Pictures (GOPs), pictures, tiles,slices, macroblocks, Coding Units (CUs), blocks, Transform Units (TUs),Prediction Units (PUs) and so forth. The entropy decoder/parser may alsoextract from the coded video sequence information such as transformcoefficients, quantizer parameter values, motion vectors, and so forth.

The parser (320) may perform entropy decoding/parsing operation on thevideo sequence received from the buffer (315), so to create symbols(321).

Reconstruction of the symbols (321) can involve multiple different unitsdepending on the type of the coded video picture or parts thereof (suchas: inter and intra picture, inter and intra block), and other factors.Which units are involved, and how, can be controlled by the subgroupcontrol information that was parsed from the coded video sequence by theparser (320). The flow of such subgroup control information between theparser (320) and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, decoder (210) can beconceptually subdivided into a number of functional units as describedbelow. In a practical implementation operating under commercialconstraints, many of these units interact closely with each other andcan, at least partly, be integrated into each other. However, for thepurpose of describing the disclosed subject matter, the conceptualsubdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit (351). Thescaler/inverse transform unit (351) receives quantized transformcoefficient as well as control information, including which transform touse, block size, quantization factor, quantization scaling matrices,etc., as symbol(s) (321) from the parser (320). It can output blockscomprising sample values, that can be input into aggregator (355).

In some cases, the output samples of the scaler/inverse transform (351)can pertain to an intra coded block; that is: a block that is not usingpredictive information from previously reconstructed pictures, but canuse predictive information from previously reconstructed parts of thecurrent picture. Such predictive information can be provided by an intrapicture prediction unit (352). In some cases, the intra pictureprediction unit (352) generates a block of the same size and shape ofthe block under reconstruction, using surrounding already reconstructedinformation fetched from the current (partly reconstructed) picture(359). The aggregator (355), in some cases, adds, on a per sample basis,the prediction information the intra prediction unit (352) has generatedto the output sample information as provided by the scaler/inversetransform unit (351).

In other cases, the output samples of the scaler/inverse transform unit(351) can pertain to an inter coded, and potentially motion compensatedblock. In such a case, a motion compensation prediction unit (353) canaccess reference picture buffer (357) memory to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols (321) pertaining to the block, these samples can beadded by the aggregator (355) to the output of the scaler/inversetransform unit (in this case called the residual samples or residualsignal) so to generate output sample information. The addresses withinthe reference picture buffer (357) memory form where the motioncompensation prediction unit (353) fetches prediction samples can becontrolled by motion vectors, available to the motion compensationprediction unit (353) in the form of symbols (321) that can have, forexample X, Y, and reference picture components. Motion compensation alsocan include interpolation of sample values as fetched from the referencepicture buffer (357) memory when sub-sample exact motion vectors are inuse, motion vector prediction mechanisms, and so forth.

The output samples of the aggregator (355) can be subject to variousloop filtering techniques in the loop filter unit (358). Videocompression technologies can include in-loop filter technologies thatare controlled by parameters included in the coded video bitstream andmade available to the loop filter unit (356) as symbols (321) from theparser (320), but can also be responsive to meta-information obtainedduring the decoding of previous (in decoding order) parts of the codedpicture or coded video sequence, as well as responsive to previouslyreconstructed and loop-filtered sample values.

The output of the loop filter unit (356) can be a sample stream that canbe output to the render device (212) as well as stored in the currentpicture memory (356) for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used asreference pictures for future prediction. Once a coded picture is fullyreconstructed and the coded picture has been identified as a referencepicture (by, for example, parser (320)), the current reference picture(359) can become part of the reference picture buffer (357), and a freshcurrent picture memory (356) can be reallocated before commencing thereconstruction of the following coded picture.

The video decoder (210) may perform decoding operations according to apredetermined video compression technology that may be documented in astandard, such as ITU-T Rec. H.265. The coded video sequence may conformto a syntax specified by the video compression technology or standardbeing used, in the sense that it adheres to the syntax of the videocompression technology or standard, as specified in the videocompression technology document or standard and specifically in theprofiles document therein. Also necessary for compliance can be that thecomplexity of the coded video sequence is within bounds as defined bythe level of the video compression technology or standard. In somecases, levels restrict the maximum picture size, maximum frame rate,maximum reconstruction sample rate (measured in, for example megasamplesper second), maximum reference picture size, and so on. Limits set bylevels can, in some cases, be further restricted through HypotheticalReference Decoder (HRD) specifications and metadata for HRD buffermanagement signaled in the coded video sequence.

In an embodiment, the receiver (310) may receive additional (redundant)data with the encoded video. The additional data may be included as partof the coded video sequence(s). The additional data may be used by thevideo decoder (320) to properly decode the data and/or to moreaccurately reconstruct the original video data. Additional data can bein the form of, for example, temporal, spatial, or SNR enhancementlayers, redundant slices, redundant pictures, forward error correctioncodes, and so on.

FIG. 4 is a functional block diagram of a video encoder (203) accordingto an embodiment of the present disclosure.

The encoder (203) may receive video samples from a video source (201)(that is not part of the encoder) that may capture video image(s) to becoded by the encoder (203).

The video source (201) may provide the source video sequence to be codedby the encoder (203) in the form of a digital video sample stream thatcan be of any suitable bit depth (for example: 8 bit, 10 bit, 12 bit, .. . ), any color space (for example, BT.601 Y CrCB, RGB, . . . ) and anysuitable sampling structure (for example Y CrCb 4:2:0, Y CrCb 4:4:4). Ina media serving system, the video source (201) may be a storage devicestoring previously prepared video. In a videoconferencing system, thevideo source (201) may be a camera that captures local image informationas a video sequence. Video data may be provided as a plurality ofindividual pictures that impart motion when viewed in sequence. Thepictures themselves may be organized as a spatial array of pixels,wherein each pixel can comprise one or more sample depending on thesampling structure, color space, etc. in use. A person skilled in theart can readily understand the relationship between pixels and samples.The description below focusses on samples.

According to an embodiment, the encoder (203) may code and compress thepictures of the source video sequence into a coded video sequence (443)in real time or under any other time constraints as required by theapplication. Enforcing appropriate coding speed is one function ofController (450). Controller controls other functional units asdescribed below and is functionally coupled to these units. The couplingis not depicted for clarity. Parameters set by controller can includerate control related parameters (picture skip, quantizer, lambda valueof rate-distortion optimization techniques, . . . ), picture size, groupof pictures (GOP) layout, maximum motion vector search range, and soforth. A person skilled in the art can readily identify other functionsof controller (450) as they may pertain to video encoder (203) optimizedfor a certain system design.

Some video encoders operate in what a person skilled in the are readilyrecognizes as a “coding loop”. As an oversimplified description, acoding loop can consist of the encoding part of an encoder (430)(“source coder” henceforth) (responsible for creating symbols based onan input picture to be coded, and a reference picture(s)), and a (local)decoder (433) embedded in the encoder (203) that reconstructs thesymbols to create the sample data a (remote) decoder also would create(as any compression between symbols and coded video bitstream islossless in the video compression technologies considered in thedisclosed subject matter). That reconstructed sample stream is input tothe reference picture memory (434). As the decoding of a symbol streamleads to bit-exact results independent of decoder location (local orremote), the reference picture buffer content is also bit exact betweenlocal encoder and remote encoder. In other words, the prediction part ofan encoder “sees”, as reference picture samples, exactly the same samplevalues as a decoder would “see” when using prediction during decoding.This fundamental principle of reference picture synchronicity (andresulting drift, if synchronicity cannot be maintained, for examplebecause of channel errors) is well known to a person skilled in the art.

The operation of the “local” decoder (433) can be the same as of a“remote” decoder (210), which has already been described in detail abovein conjunction with FIG. 3 . Briefly referring also to FIG. 3 , however,as symbols are available and encoding/decoding of symbols to a codedvideo sequence by entropy coder (445) and parser (320) can be lossless,the entropy decoding parts of decoder (210), including channel (312),receiver (310), buffer (315), and parser (320) may not be fullyimplemented in local decoder (433).

An observation that can be made at this point is that any decodertechnology except the parsing/entropy decoding that is present in adecoder also necessarily needs to be present, in substantially identicalfunctional form, in a corresponding encoder. For this reason, thedisclosed subject matter focusses on decoder operation. The descriptionof encoder technologies can be abbreviated as they are the inverse ofthe comprehensively described decoder technologies. Only in certainareas a more detail description is required and provided below.

As part of its operation, the source coder (430) may perform motioncompensated predictive coding, which codes an input frame predictivelywith reference to one or more previously-coded frames from the videosequence that were designated as “reference frames.” In this manner, thecoding engine (432) codes differences between pixel blocks of an inputframe and pixel blocks of reference frame(s) that may be selected asprediction reference(s) to the input frame.

The local video decoder (433) may decode coded video data of frames thatmay be designated as reference frames, based on symbols created by thesource coder (430). Operations of the coding engine (432) mayadvantageously be lossy processes. When the coded video data may bedecoded at a video decoder (not shown in FIG. 4 ), the reconstructedvideo sequence typically may be a replica of the source video sequencewith some errors. The local video decoder (433) replicates decodingprocesses that may be performed by the video decoder on reference framesand may cause reconstructed reference frames to be stored in thereference picture cache (434). In this manner, the encoder (203) maystore copies of reconstructed reference frames locally that have commoncontent as the reconstructed reference frames that will be obtained by afar-end video decoder (absent transmission errors).

The predictor (435) may perform prediction searches for the codingengine (432). That is, for a new frame to be coded, the predictor (435)may search the reference picture memory (434) for sample data (ascandidate reference pixel blocks) or certain metadata such as referencepicture motion vectors, block shapes, and so on, that may serve as anappropriate prediction reference for the new pictures. The predictor(435) may operate on a sample block-by-pixel block basis to findappropriate prediction references. In some cases, as determined bysearch results obtained by the predictor (435), an input picture mayhave prediction references drawn from multiple reference pictures storedin the reference picture memory (434).

The controller (450) may manage coding operations of the video coder(430), including, for example, setting of parameters and subgroupparameters used for encoding the video data.

Output of all aforementioned functional units may be subjected toentropy coding in the entropy coder (445). The entropy coder translatesthe symbols as generated by the various functional units into a codedvideo sequence, by loss-less compressing the symbols according totechnologies known to a person skilled in the art as, for exampleHuffman coding, variable length coding, arithmetic coding, and so forth.

The transmitter (440) may buffer the coded video sequence(s) as createdby the entropy coder (445) to prepare it for transmission via acommunication channel (460), which may be a hardware/software link to astorage device which would store the encoded video data. The transmitter(440) may merge coded video data from the video coder (430) with otherdata to be transmitted, for example, coded audio data and/or ancillarydata streams (sources not shown).

The controller (450) may manage operation of the encoder (203). Duringcoding, the controller (450) may assign to each coded picture a certaincoded picture type, which may affect the coding techniques that may beapplied to the respective picture. For example, pictures often may beassigned as one of the following frame types:

An Intra Picture (I picture) may be one that may be coded and decodedwithout using any other frame in the sequence as a source of prediction.Some video codecs allow for different types of Intra pictures,including, for example Independent Decoder Refresh Pictures. A personskilled in the art is aware of those variants of I pictures and theirrespective applications and features.

A Predictive picture (P picture) may be one that may be coded anddecoded using intra prediction or inter prediction using at most onemotion vector and reference index to predict the sample values of eachblock.

A Bi-directionally Predictive Picture (B Picture) may be one that may becoded and decoded using intra prediction or inter prediction using atmost two motion vectors and reference indices to predict the samplevalues of each block. Similarly, multiple-predictive pictures can usemore than two reference pictures and associated metadata for thereconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality ofsample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 sampleseach) and coded on a block-by-block basis. Blocks may be codedpredictively with reference to other (already coded) blocks asdetermined by the coding assignment applied to the blocks' respectivepictures. For example, blocks of I pictures may be codednon-predictively or they may be coded predictively with reference toalready coded blocks of the same picture (spatial prediction or intraprediction). Pixel blocks of P pictures may be coded non-predictively,via spatial prediction or via temporal prediction with reference to onepreviously coded reference pictures. Blocks of B pictures may be codednon-predictively, via spatial prediction or via temporal prediction withreference to one or two previously coded reference pictures.

The video encoder (203) may perform coding operations according to apredetermined video coding technology or standard, such as ITU-T Rec.H.265. In its operation, the video encoder (203) may perform variouscompression operations, including predictive coding operations thatexploit temporal and spatial redundancies in the input video sequence.The coded video data, therefore, may conform to a syntax specified bythe video coding technology or standard being used.

In an embodiment, the transmitter (440) may transmit additional datawith the encoded video. The source coder (430) may include such data aspart of the coded video sequence. Additional data may comprisetemporal/spatial/SNR enhancement layers, other forms of redundant datasuch as redundant pictures and slices, Supplementary EnhancementInformation (SEI) messages, Visual Usability Information (VUI) parameterset fragments, and so on.

Before describing certain aspects of the disclosed subject matter inmore detail, a few terms need to be introduced that will be referred toin the remainder of this description.

Sub-Picture henceforth refers to an, in some cases, rectangulararrangement of samples, blocks, macroblocks, coding units, or similarentities that are semantically grouped, and that may be independentlycoded in changed resolution. One or more sub-pictures may for a picture.One or more coded sub-pictures may form a coded picture. One or moresub-pictures may be assembled into a picture, and one or more subpictures may be extracted from a picture. In certain environments, oneor more coded sub-pictures may be assembled in the compressed domainwithout transcoding to the sample level into a coded picture, and in thesame or certain other cases, one or more coded sub-pictures may beextracted from a coded picture in the compressed domain.

Adaptive Resolution Change (ARC) henceforth refers to mechanisms thatallow the change of resolution of a picture or sub-picture within acoded video sequence, by the means of, for example, reference pictureresampling. ARC parameters henceforth refer to the control informationrequired to perform adaptive resolution change, that may include, forexample, filter parameters, scaling factors, resolutions of outputand/or reference pictures, various control flags, and so forth.

Above description is focused on coding and decoding a single,semantically independent coded video picture. Before describing theimplication of coding/decoding of multiple sub pictures with independentARC parameters and its implied additional complexity, options forsignaling ARC parameters shall be described.

Referring to FIG. 5B, several novel options for signaling ARC parametersare shown. As noted with each of the options, they have certainadvantages and certain disadvantages from a coding efficiency,complexity, and architecture viewpoint. A video coding standard ortechnology may choose one or more of these options, or options knownfrom previous art, for signaling ARC parameters. The options may not bemutually exclusive, and conceivably may be interchanged based onapplication needs, standards technology involved, or encoder's choice.

Classes of ARC parameters may include:

-   -   up/downsample factors, separate or combined in X and Y dimension    -   up/downsample factors, with an addition of a temporal dimension,        indicating constant speed zoom in/out for a given number of        pictures    -   Either of the above two may involve the coding of one or more        presumably short syntax elements that may point into a table        containing the factor(s).    -   resolution, in X or Y dimension, in units of samples, blocks,        macroblocks, CUs, or any other suitable granularity, of the        input picture, output picture, reference picture, coded picture,        combined or separately. If there is more than one resolution        (such as, for example, one for input picture, one for reference        picture) then, in certain cases, one set of values may be        inferred to from another set of values. Such could be gated, for        example, by the use of flags. For a more detailed example, see        below.    -   “warping” coordinates akin those used in H.263 Annex P, again in        a suitable granularity as described above. H.263 Annex P defines        one efficient way to code such warping coordinates, but other,        potentially more efficient ways could conceivably also be        devised. For example, the variable length reversible,        “Huffman”-style coding of warping coordinates of Annex P could        be replaced by a suitable length binary coding, where the length        of the binary code word could, for example, be derived from a        maximum picture size, possibly multiplied by a certain factor        and offset by a certain value, so to allow for “warping” outside        of the maximum picture size's boundaries.    -   upsample or downsample filter parameters. In the easiest case,        there may be only a single filter for upsample and/or        downsampling. However, in certain cases, it can be advantageous        to allow more flexibility in filter design, and that may require        to signaling of filter parameters. Such parameters may be        selected through an index in a list of possible filter designs,        the filter may be fully specified (for example through a list of        filter coefficients, using suitable entropy coding techniques),        the filter may be implicitly selected through up/downsample        ratios according which in turn are signaled according to any of        the mechanisms mentioned above, and so forth.

Henceforth, the description assumes the coding of a finite set ofup/downsample factors (the same factor to be used in both X and Ydimension), indicated through a codeword. That codeword canadvantageously be variable length coded, for example using theExt-Golomb code common for certain syntax elements in video codingspecifications such as H.264 and H.265. One suitable mapping of valuesto up/downsample factors can, for example, be according to the followingTable 1:

TABLE 1 Codeword Ext-Golomb Code Original/Target resolution 0 1 1/1 1010 1/1.5 (upscale by 50%) 2 011 1.5/1 (downscale by 50%) 3 00100 1/2(upscale by 100%) 4 00101 2/1 (downscale by 100%)

Many similar mappings could be devised according to the needs of anapplication and the capabilities of the up and downscale mechanismsavailable in a video compression technology or standard. The table couldbe extended to more values. Values may also be represented by entropycoding mechanisms other than Ext-Golomb codes, for example using binarycoding. That may have certain advantages when the resampling factorswere of interest outside the video processing engines (encoder anddecoder foremost) themselves, for example by MANES. It should be notedthat, for the (presumably) most common case where no resolution changeis required, an Ext-Golomb code can be chosen that is short; in thetable above, only a single bit. That can have a coding efficiencyadvantage over using binary codes for the most common case.

The number of entries in the table, as well as their semantics may befully or partially configurable. For example, the basic outline of thetable may be conveyed in a “high” parameter set such as a sequence ordecoder parameter set. Alternatively or in addition, one or more suchtables may be defined in a video coding technology or standard, and maybe selected through for example a decoder or sequence parameter set.

Henceforth, we describe how an upsample/downsample factor (ARCinformation), coded as described above, may be included in a videocoding technology or standard syntax. Similar considerations may applyto one, or a few, codewords controlling up/downsample filters. See belowfor a discussion when comparatively large amounts of data are requiredfor a filter or other data structures.

FIG. 5A shows H.263 Annex P (500 a) which includes the ARC information502 in the form of four warping coordinates into the picture header 501,specifically in the H.263 Annex P (503) header extension. This can be asensible design choice when a) there is a picture header available, andb) frequent changes of the ARC information are expected. However, theoverhead when using H.263-style signaling can be quite high, and scalingfactors may not pertain among picture boundaries as picture header canbe of transient nature.

FIG. 5A also shows JVCET-M135-v1 (500 b), cited above, which includesthe ARC reference information (505) (an index) located in a pictureparameter set (504), indexing a table (506) including target resolutionsthat in turn is located inside a sequence parameter set (507). Theplacement of the possible resolution in a table (506) in the sequenceparameter set (SPS) (507) can, according to verbal statements made bythe authors, be justified by using the SPS as an interoperabilitynegotiation point during capability exchange. Resolution can change,within the limits set by the values in the table (506) from picture topicture by referencing the appropriate picture parameter set (PPS)(504).

With respect to FIG. 5B, the following additional options may exist toconvey ARC information in a video bitstream. Each of these options hascertain advantages over existing art as described above. The options maybe simultaneously present in the same video coding technology orstandard.

In an embodiment, ARC information (509) such as a resampling (zoom)factor may be present in a slice header, a group of blocks (GOB) header,a tile header, or a tile group header (tile group header henceforth)(508). This can be adequate if the ARC information is small, such as asingle variable length ue(v) or fixed length codeword of a few bits, forexample as shown in Table 1 above. Having the ARC information in a tilegroup header directly has the additional advantage if the ARCinformation may be applicable to a sub picture represented by, forexample, that tile group, rather than the whole picture. See also below.In addition, even if the video compression technology or standardenvisions only whole picture adaptive resolution changes (in contrastto, for example, tile group based adaptive resolution changes), puttingthe ARC information into the tile group header vis a vis putting it intoan H.263-style picture header has certain advantages from an errorresilience viewpoint.

In the same or another embodiment, the ARC information (512) itself maybe present in an appropriate parameter set (511) such as, for example, apicture parameter set, header parameter set, tile parameter set,adaptation parameter set (APS), and so forth (adaptation parameter setdepicted). The scope of that parameter set can advantageously be nolarger than a picture, for example a tile group. The use of the ARCinformation is implicit through the activation of the relevant parameterset. For example, when a video coding technology or standardcontemplates only picture-based ARC, then a picture parameter set orequivalent may be appropriate.

In the same or another embodiment, ARC reference information (513) maybe present in a Tile Group header (514) or a similar data structure.That reference information (513) can refer to a subset of ARCinformation (515) available in a parameter set (516) with a scope beyonda single picture, for example a sequence parameter set, or decoderparameter set.

The additional level of indirection implied activation of a PPS from atile group header, PPS, SPS, as used in JVET-M0135-v1 appears to beunnecessary, as picture parameter sets, just as sequence parameter sets,can (and have in certain standards such as RFC3984) be used forcapability negotiation or announcements. If, however, the ARCinformation should be applicable to a sub picture represented, forexample, by a tile groups also, a parameter set with an activation scopelimited to a tile group, such as the adaptation parameter set or aheader parameter set may be the better choice. Also, if the ARCinformation is of more than negligible size—for example contains filtercontrol information such as numerous filter coefficients—then aparameter may be a better choice than using a header (508) directly froma coding efficiency viewpoint, as those settings may be reusable byfuture pictures or sub-pictures by referencing the same parameter set.

When using the sequence parameter set or another higher parameter setwith a scope spanning multiple pictures, certain considerations mayapply:

-   -   1. The parameter set to store the ARC information table can, in        some cases, be the sequence parameter set (516), but in other        cases advantageously the decoder parameter set. The decoder        parameter set can have an activation scope of multiple CVSs,        namely the coded video stream, i.e. all coded video bits from        session start until session teardown. Such a scope may be more        appropriate because possible ARC factors may be a decoder        feature, possibly implemented in hardware, and hardware features        tend not to change with any CVS (which in at least some        entertainment systems is a Group of Pictures, one second or less        in length). That said, putting the table into the sequence        parameter set is expressly included in the placement options        described herein, in particular in conjunction with point 2        below.    -   2. The ARC reference information (513) may advantageously be        placed directly into the picture/slice tile/group of blocks        (GOB)/tile group header (tile group header henceforth) (514)        rather than into the picture parameter set as in JVCET-M0135-v1,        The reason is as follows: when an encoder wants to change a        single value in a picture parameter set, such as for example the        ARC reference information, then it has to create a new PPS and        reference that new PPS. Assume that only the ARC reference        information changes, but other information such as, for example,        the quantization matrix information in the PPS stays. Such        information can be of substantial size, and would need to be        retransmitted to make the new PPS complete. As the ARC reference        information may be a single codeword, such as the index into the        ARC reference table and that would be the only value that        changes, it would be cumbersome and wasteful to retransmit all        the, for example, quantization matrix information. Accordingly,        the data structures of FIG. 5B can be considerably better from a        coding efficiency viewpoint to avoid the indirection through the        PPS, as proposed in JVET-M0135-v1. Similarly, putting the ARC        reference information into the PPS has the additional        disadvantage that the ARC information referenced by the ARC        reference information (513) necessarily needs to apply to the        whole picture and not to a sub-picture, as the scope of a        picture parameter set activation is a picture.

In the same or another embodiment, the signaling of ARC parameters canfollow a detailed example as outlined in FIG. 6 . FIG. 6 depicts syntaxdiagrams in a representation as used in video coding standards since atleast 1993. The notation of such syntax diagrams roughly follows C-styleprogramming. Lines in boldface indicate syntax elements present in thebitstream, lines without boldface often indicate control flow or thesetting of variables.

A tile group header (601) as an exemplary syntax structure of a headerapplicable to a (possibly rectangular) part of a picture canconditionally contain, a variable length, Exp-Golomb coded syntaxelement dec_pic_size_idx (602) (depicted in boldface). The presence ofthis syntax element in the tile group header can be gated on the use ofadaptive resolution (603). Here, the value of a flag is not depicted inboldface, which means that flag is present in the bitstream at the pointwhere it occurs in the syntax diagram. Whether or not adaptiveresolution is in use for this picture or parts thereof can be signaledin any high level syntax structure inside or outside the bitstream. Inthe example shown, it is signaled in the sequence parameter set asoutlined below.

Still referring to FIG. 6 , an excerpt of a sequence parameter set (610)is also shown. The first syntax element shown isadaptive_pic_resolution_change_flag (611). When true, that flag canindicate the use of adaptive resolution which, in turn may requirecertain control information. In the example, such control information isconditionally present based on the value of the flag based on the if( )statement in the parameter set (612) and the tile group header (601).

When adaptive resolution is in use, in this example, an outputresolution is coded in units of samples (613). The numeral (613) refersto both output_pic_width_in_luma_samples andoutput_pic_height_in_luma_samples, which together can define theresolution of the output picture. Elsewhere in a video coding technologyor standard, certain restrictions to either value can be defined. Forexample, a level definition may limit the number of total outputsamples, which could be the product of the value of those two syntaxelements. Also, certain video coding technologies or standards, orexternal technologies or standards such as, for example, systemstandards, may limit the numbering range (for example, one or bothdimensions must be divisible by a power of 2 number), or the aspectratio (for example, the width and height must be in a relation such as4:3 or 16:9). Such restrictions may be introduced to facilitate hardwareimplementations or for other reasons, and are well known in the art.

In certain applications, it can be advisable that the encoder instructsthe decoder to use a certain reference picture size rather thanimplicitly assume that size to be the output picture size. In thisexample, the syntax element reference_pic_size_present_flag (614) gatesthe conditional presence of reference picture dimensions (615) (again,the numeral refers to both width and height).

Finally, a table of possible decoding picture width and heights isshown. Such a table can be expressed, for example, by a table indication(num_dec_pic_size_in_luma_samples_minus1) (616). The “minus1” can referto the interpretation of the value of that syntax element. For example,if the coded value is zero, one table entry is present. If the value isfive, six table entries are present. For each “line” in the table,decoded picture width and height are then included in the syntax (617).

The table entries presented (617) can be indexed using the syntaxelement dec_pic_size_idx (602) in the tile group header, therebyallowing different decoded sizes—in effect, zoom factors—per tile group.

Certain video coding technologies or standards, for example VP9, supportspatial scalability by implementing certain forms of reference pictureresampling (signaled quite differently from the disclosed subjectmatter) in conjunction with temporal scalability, so to enable spatialscalability. In particular, certain reference pictures may be upsampledusing ARC-style technologies to a higher resolution to form the base ofa spatial enhancement layer. Those upsampled pictures could be refined,using normal prediction mechanisms at the high resolution, so to adddetail.

The disclosed subject matter can be used in such an environment. Incertain cases, in the same or another embodiment, a value in the networkabstract layer (NAL) unit header, for example the Temporal ID field, canbe used to indicate not only the temporal but also the spatial layer.Doing so has certain advantages for certain system designs; for example,existing Selected Forwarding Units (SFU) created and optimized fortemporal layer selected forwarding based on the NAL unit header TemporalID value can be used without modification, for scalable environments. Inorder to enable that, there may be a requirement for a mapping betweenthe coded picture size and the temporal layer that is indicated by thetemporal ID field in the NAL unit header.

In some video coding technologies, an access unit (AU) can refer tocoded picture(s), slice(s), tile(s), NAL Unit(s), and so forth, thatwere captured and composed into a the respective picture/slice/tile/NALunit bitstream at a given instance in time. That instance in time can bethe composition time.

In HEVC, and certain other video coding technologies, a picture ordercount (POC) value can be used for indicating a selected referencepicture among multiple reference pictures stored in a decoded picturebuffer (DPB). When a single access unit (AU) includes one or morepictures, slices, or tiles, each picture, slice, or tile, the respectivedata may carry the same POC value, from which it can be derived thatthey were created from content of the same composition time. In otherwords, in a scenario where two pictures/slices/tiles carry the samegiven POC value, that can be indicative of the two picture/slice/tilebelonging to the same AU and having the same composition time.Conversely, two pictures/tiles/slices having different POC values canindicate those pictures/slices/tiles belonging to different AUs andhaving different composition times.

In an embodiment of the disclosed subject matter, aforementioned rigidrelationship can be relaxed in that an access unit can comprisepictures, slices, or tiles with different POC values. By allowingdifferent POC values within an AU, it becomes possible to use the POCvalue to identify potentially independently decodablepictures/slices/tiles with identical presentation time. That, in turn,can enable support of multiple scalable layers without a change ofreference picture selection signaling (e.g. reference picture setsignaling or reference picture list signaling), as described in moredetail below.

It is, however, still desirable to be able to identify the AU apicture/slice/tile belongs to, with respect to otherpicture/slices/tiles having different POC values, from the POC valuealone. This can be achieved, as described below.

In the same or other embodiments, an access unit count (AUC) may besignaled in a high-level syntax structure, such as NAL unit header,slice header, tile group header, SEI message, parameter set or AUdelimiter. The value of AUC may be used to identify which NAL units,pictures, slices, or tiles belong to a given AU. The value of AUC may becorresponding to a distinct composition time instance. The AUC value maybe equal to a multiple of the POC value. By diving the POC value by aninteger value, the AUC value may be calculated. In certain cases,division operations can place a certain burden on decoderimplementations. In such cases, small restrictions in the numberingspace of the AUC values may allow to substitute the division operationby shift operations. For example, the AUC value may be equal to a MostSignificant Bit (MSB) value of the POC value range.

In the same embodiment, a value of POC cycle per AU (poc_cycle_au) maybe signaled in a high-level syntax structure, such as NAL unit header,slice header, tile group header, SEI message, parameter set or AUdelimiter. The poc_cycle_au may indicate how many different andconsecutive POC values can be associated with the same AU. For example,if the value of poc_cycle_au is equal to 4, the pictures, slices ortiles with the POC value equal to 0-3, inclusive, are associated withthe AU with AUC value equal to 0, and the pictures, slices or tiles withPOC value equal to 4-7, inclusive, are associated with the AU with AUCvalue equal to 1. Hence, the value of AUC may be inferred by dividingthe POC value by the value of poc_cycle_au.

In the same or another embodiment, the value of poc_cycle_au may bederived from information, located for example in the video parameter set(VPS), that identifies the number of spatial or SNR layers in a codedvideo sequence. Such a possible relationship is briefly described below.While the derivation as described above may save a few bits in the VPSand hence may improves coding efficiency, it can be advantageous toexplicitly code poc_cycle_au in an appropriate high level syntaxstructure hierarchically below the video parameter set, so to be able tominimize poc_cycle_au for a given small part of a bitstream such as apicture. This optimization may save more bits than can be saved throughthe derivation process above because POC values (and/or values of syntaxelements indirectly referring to POC) may be coded in low level syntaxstructures.

In the same or another embodiment, shown in FIG. 9 , provides an exampleof syntax tables to signal the syntax element of vps_poc_cycle_au in VPS(or SPS), which indicates the poc_cycle_au used for all picture/slicesin a coded video sequence, and the syntax element of slice_poc_cycle_au,which indicates the poc_cycle_au of the current slice, in slice header.If the POC value increases uniformly per AU,vps_contant_poc_cycle_per_au in VPS is set equal to 1 andvps_poc_cycle_au is signaled in VPS. In this case, slice_poc_cycle_au isnot explicitly signaled, and the value of AUC for each AU is calculatedby dividing the value of POC by vps_poc_cycle_au. If the POC value doesnot increase uniformly per AU, vps_contant_poc_cycle_per_au in VPS isset equal to 0. In this case, vps_access_unit_cnt is not signaled, whileslice_access_unit_cnt is signaled in slice header for each slice orpicture. Each slice or picture may have a different value ofslice_access_unit_cnt. The value of AUC for each AU is calculated bydividing the value of POC by slice_poc_cycle_au.

FIG. 10 is a flow chart illustrating the above discussed example process(1000) of decoding POC cycle per access unit and access unit countvalue. As shown in FIG. 10 , process (1000) may include parsing VPS/SPSand identifying whether a spread between the minimum and maximum POCvalues per AU varies or is constant (block 1010).

As shown in FIG. 10 , process (1000) may include determining if thespread between the minimum and maximum POC values per AU is constantwithin a CVS (block 1020). If the spread is constant, a value of the AUCis calculated by dividing the value of POC by vps_poc_cycle_au (block1030). If the spread is variable, a value of the AUC is calculated bydividing the value of POC by slice_poc_cycle_au (block 1040). In someembodiments, the result of the calculations may be rounded down to thenearest integer to obtain the value of the AUC.

In the same or other embodiments, even though the value of POC of apicture, slice, or tile may be different, the picture, slice, or tilecorresponding to an AU with the same AUC value may be associated withthe same decoding or output time instance. Hence, without anyinter-parsing/decoding dependency across pictures, slices or tiles inthe same AU, all or subset of pictures, slices or tiles associated withthe same AU may be decoded in parallel, and may be outputted at the sametime instance.

In the same or other embodiments, even though the value of POC of apicture, slice, or tile may be different, the picture, slice, or tilecorresponding to an AU with the same AUC value may be associated withthe same composition/display time instance. When the composition time iscontained in a container format, even though pictures correspond todifferent AUs, if the pictures have the same composition time, thepictures can be displayed at the same time instance.

In the same or other embodiments, each picture, slice, or tile may havethe same temporal identifier (temporal_id) in the same AU. All or subsetof pictures, slices or tiles corresponding to a time instance may beassociated with the same temporal sub-layer. In the same or otherembodiments, each picture, slice, or tile may have the same or adifferent spatial layer id (layer_id) in the same AU. All or subset ofpictures, slices or tiles corresponding to a time instance may beassociated with the same or a different spatial layer.

FIG. 8 shows an example of a video sequence structure with combinationof temporal_id (TID), layer_id (LID), POC and AUC values with adaptiveresolution change. In this example, a picture, slice or tile in thefirst AU with AUC=0 may have temporal_id=0 and layer_id=0 or 1, while apicture, slice or tile in the second AU with AUC=1 may havetemporal_id=1 and layer_id=0 or 1, respectively. The value of POC isincreased by 1 per picture regardless of the values of temporal_id andlayer_id. In this example, the value of poc_cycle_au can be equal to 2.Preferably, the value of poc_cycle_au may be set equal to the number of(spatial scalability) layers. In this example, hence, the value of POCis increased by 2, while the value of AUC is increased by 1.

In the above embodiments, all or a sub-set of inter-picture orinter-layer prediction structure and reference picture indication may besupported by using the existing reference picture set (RPS) signaling inHEVC or the reference picture list (RPL) signaling. In RPS or RPL, theselected reference picture is indicated by signaling the value of POC orthe delta value of POC between the current picture and the selectedreference picture. For the disclosed subject matter, the RPS and RPL canbe used to indicate the inter-picture or inter-layer predictionstructure without change of signaling, but with the followingrestrictions. If the value of temporal_id of a reference picture isgreater than the value of temporal_id current picture, the currentpicture may not use the reference picture for motion compensation orother predictions. If the value of layer_id of a reference picture isgreater than the value of layer_id current picture, the current picturemay not use the reference picture for motion compensation or otherpredictions.

In the same or other embodiments, the motion vector scaling based on POCdifference for temporal motion vector prediction may be disabled acrossmultiple pictures within an access unit. Hence, although each picturemay have a different POC value within an access unit, the motion vectoris not scaled and used for temporal motion vector prediction within anaccess unit. This is because a reference picture with a different POC inthe same AU is considered a reference picture having the same timeinstance. Therefore, in the embodiment, the motion vector scalingfunction may return 1, when the reference picture belongs to the AUassociated with the current picture.

In the same and other embodiments, the motion vector scaling based onPOC difference for temporal motion vector prediction may be optionallydisabled across multiple pictures, when the spatial resolution of thereference picture is different from the spatial resolution of thecurrent picture. When the motion vector scaling is allowed, the motionvector is scaled based on both POC difference and the spatial resolutionratio between the current picture and the reference picture.

In the same or another embodiment, the motion vector may be scaled basedon AUC difference instead of POC difference, for temporal motion vectorprediction, especially when the poc_cycle_au has non-uniform value (whenvps_contant_poc_cycle_per_au==0). Otherwise (whenvps_contant_poc_cycle_per_au==1), the motion vector scaling based on AUCdifference may be identical to the motion vector scaling based on POCdifference.

In the same or another embodiment, when the motion vector is scaledbased on AUC difference, the reference motion vector in the same AU(with the same AUC value) with the current picture is not scaled basedon AUC difference and used for motion vector prediction without scalingor with scaling based on spatial resolution ratio between the currentpicture and the reference picture.

In the same and other embodiments, the AUC value is used for identifyingthe boundary of AU and used for hypothetical reference decoder (HRD)operation, which needs input and output timing with AU granularity. Inmost cases, the decoded picture with the highest layer in an AU may beoutputted for display. The AUC value and the layer id value can be usedfor identifying the output picture.

The techniques for signaling adaptive resolution parameters describedabove, can be implemented as computer software using computer-readableinstructions and physically stored in one or more computer-readablemedia. For example, FIG. 7 shows a computer system 700 suitable forimplementing certain embodiments of the disclosed subject matter.

The computer software can be coded using any suitable machine code orcomputer language, that may be subject to assembly, compilation,linking, or like mechanisms to create code comprising instructions thatcan be executed directly, or through interpretation, micro-codeexecution, and the like, by computer central processing units (CPUs),Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers orcomponents thereof, including, for example, personal computers, tabletcomputers, servers, smartphones, gaming devices, internet of thingsdevices, and the like.

The components shown in FIG. 7 for computer system 700 are exemplary innature and are not intended to suggest any limitation as to the scope ofuse or functionality of the computer software implementing embodimentsof the present disclosure. Neither should the configuration ofcomponents be interpreted as having any dependency or requirementrelating to any one or combination of components illustrated in theexemplary embodiment of a computer system 700.

Computer system 700 may include certain human interface input devices.Such a human interface input device may be responsive to input by one ormore human users through, for example, tactile input (such as:keystrokes, swipes, data glove movements), audio input (such as: voice,clapping), visual input (such as: gestures), olfactory input (notdepicted). The human interface devices can also be used to capturecertain media not necessarily directly related to conscious input by ahuman, such as audio (such as: speech, music, ambient sound), images(such as: scanned images, photographic images obtain from a still imagecamera), video (such as two-dimensional video, three-dimensional videoincluding stereoscopic video).

Input human interface devices may include one or more of (only one ofeach depicted): keyboard 701, mouse 702, trackpad 703, touch screen 710,data-glove 704, joystick 705, microphone 706, scanner 707, camera 708.

Computer system 700 may also include certain human interface outputdevices. Such human interface output devices may be stimulating thesenses of one or more human users through, for example, tactile output,sound, light, and smell/taste. Such human interface output devices mayinclude tactile output devices (for example tactile feedback by thetouch-screen 710, data-glove 704, or joystick 705, but there can also betactile feedback devices that do not serve as input devices), audiooutput devices (such as: speakers 709, headphones (not depicted)),visual output devices (such as screens 710 to include CRT screens, LCDscreens, plasma screens, OLED screens, each with or without touch-screeninput capability, each with or without tactile feedback capability—someof which may be capable to output two dimensional visual output or morethan three dimensional output through means such as stereographicoutput; virtual-reality glasses (not depicted), holographic displays andsmoke tanks (not depicted)), and printers (not depicted).

Computer system 700 can also include human accessible storage devicesand their associated media such as optical media including CD/DVD ROM/RW720 with CD/DVD or the like media 721, thumb-drive 722, removable harddrive or solid state drive 723, legacy magnetic media such as tape andfloppy disc (not depicted), specialized ROM/ASIC/PLD based devices suchas security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computerreadable media” as used in connection with the presently disclosedsubject matter does not encompass transmission media, carrier waves, orother transitory signals.

Computer system 700 can also include interface to one or morecommunication networks. Networks can for example be wireless, wireline,optical. Networks can further be local, wide-area, metropolitan,vehicular and industrial, real-time, delay-tolerant, and so on. Examplesof networks include local area networks such as Ethernet, wireless LANs,cellular networks to include GSM, 3G, 4G, 5G, LTE and the like, TVwireline or wireless wide area digital networks to include cable TV,satellite TV, and terrestrial broadcast TV, vehicular and industrial toinclude CANBus, and so forth. Certain networks commonly require externalnetwork interface adapters that attached to certain general purpose dataports or peripheral buses (749) (such as, for example USB ports of thecomputer system 700; others are commonly integrated into the core of thecomputer system 700 by attachment to a system bus as described below(for example Ethernet interface into a PC computer system or cellularnetwork interface into a smartphone computer system). Using any of thesenetworks, computer system 700 can communicate with other entities. Suchcommunication can be uni-directional, receive only (for example,broadcast TV), uni-directional send-only (for example CANbus to certainCANbus devices), or bi-directional, for example to other computersystems using local or wide area digital networks. Certain protocols andprotocol stacks can be used on each of those networks and networkinterfaces as described above.

Aforementioned human interface devices, human-accessible storagedevices, and network interfaces can be attached to a core 740 of thecomputer system 700.

The core 740 can include one or more Central Processing Units (CPU) 741,Graphics Processing Units (GPU) 742, specialized programmable processingunits in the form of Field Programmable Gate Areas (FPGA) 743, hardwareaccelerators for certain tasks 744, and so forth. These devices, alongwith Read-only memory (ROM) 745, Random-access memory 746, internal massstorage such as internal non-user accessible hard drives, SSDs, and thelike 747, may be connected through a system bus 748. In some computersystems, the system bus 748 can be accessible in the form of one or morephysical plugs to enable extensions by additional CPUs, GPU, and thelike. The peripheral devices can be attached either directly to thecore's system bus 748, or through a peripheral bus 749. Architecturesfor a peripheral bus include PCI, USB, and the like.

CPUs 741, GPUs 742, FPGAs 743, and accelerators 744 can execute certaininstructions that, in combination, can make up the aforementionedcomputer code. That computer code can be stored in ROM 745 or RAM 746.Transitional data can be also be stored in RAM 746, whereas permanentdata can be stored for example, in the internal mass storage 747. Faststorage and retrieve to any of the memory devices can be enabled throughthe use of cache memory, that can be closely associated with one or moreCPU 741, GPU 742, mass storage 747, ROM 745, RAM 746, and the like.

The computer readable media can have computer code thereon forperforming various computer-implemented operations. The media andcomputer code can be those specially designed and constructed for thepurposes of the present disclosure, or they can be of the kind wellknown and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system havingarchitecture 700, and specifically the core 740 can providefunctionality as a result of processor(s) (including CPUs, GPUs, FPGA,accelerators, and the like) executing software embodied in one or moretangible, computer-readable media. Such computer-readable media can bemedia associated with user-accessible mass storage as introduced above,as well as certain storage of the core 740 that are of non-transitorynature, such as core-internal mass storage 747 or ROM 745. The softwareimplementing various embodiments of the present disclosure can be storedin such devices and executed by core 740. A computer-readable medium caninclude one or more memory devices or chips, according to particularneeds. The software can cause the core 740 and specifically theprocessors therein (including CPU, GPU, FPGA, and the like) to executeparticular processes or particular parts of particular processesdescribed herein, including defining data structures stored in RAM 746and modifying such data structures according to the processes defined bythe software. In addition or as an alternative, the computer system canprovide functionality as a result of logic hardwired or otherwiseembodied in a circuit (for example: accelerator 744), which can operatein place of or together with software to execute particular processes orparticular parts of particular processes described herein. Reference tosoftware can encompass logic, and vice versa, where appropriate.Reference to a computer-readable media can encompass a circuit (such asan integrated circuit (IC)) storing software for execution, a circuitembodying logic for execution, or both, where appropriate. The presentdisclosure encompasses any suitable combination of hardware andsoftware.

While this disclosure has described several exemplary embodiments, thereare alterations, permutations, and various substitute equivalents, whichfall within the scope of the disclosure. It will thus be appreciatedthat those skilled in the art will be able to devise numerous systemsand methods which, although not explicitly shown or described herein,embody the principles of the disclosure and are thus within the spiritand scope thereof.

Acronyms:

Access Unit (AU)

Access Unit Count (AUC)

Adaptive Resolution Change (ARC)

Coding Unit (CU)

Group of Pictures (GOP)

High Efficiency Video Coding (HEVC)

Hypothetical Reference Decoder (HRD)

Most Significant Bit (MSB)

Network Abstract Layer (NAL)

Picture Order Count (POC)

Reference Picture Set (RPS)

Sequence Parameter Set (SPS)

Supply Enhancement Information (SEI)

Video Parameter Set (VPS)

The invention claimed is:
 1. A method for video encoding, comprising:encoding, to a coded video sequence, at least one of a first picture, afirst slice, and a first tile with a first value of a picture ordercount; and encoding, to the coded video sequence, at least one of asecond picture, a second slice, and a second tile with a second value ofthe picture order count, wherein the at least one of the first picture,the first slice, and the first tile belong to a first access unit amongaccess units, and the at least one of the second picture, the secondslice, and the second tile belong to the first access unit, wherein thefirst value of the picture order count and the second value of thepicture order count are different, and wherein the first access unitcorresponds to a time instance; and encoding, to a high level syntaxstructure, a syntax element poc_cycle_au, wherein a value of thepoc_cycle_au corresponds to a number indicating how many picture ordercount values are associated with the first access unit and a maximumdifference between the first value of the picture order count and thesecond value of the picture order count in the first access unit.
 2. Themethod of claim 1, further comprising: encoding, to the high levelsyntax structure, a syntax element vp_spoc_cycle_au, wherein a value ofvp_spoc_cycle_au is indicative of all coded pictures or slices in acoded video sequence; and encoding, to the high level syntax structure,a syntax element slice_poc_cycle_au, wherein a value ofslice_poc_cycle_au is indicative of the poc_cycle_au of a current slice.3. The method of claim 1, further comprising: based on poc_cycle_aubeing constant for each access unit in the coded video sequence,encoding, to the high level syntax structure, avps_constant_poc_cycle_per_au equaling 1; and based on poc_cycle_aubeing variable for each access unit in the coded video sequence,encoding, to the high level syntax structure, avps_constant_poc_cycle_per_au equaling
 0. 4. The method of claim 2,wherein the high level syntax structure is a video parameter set or asequence parameter set.
 5. The method of claim 1, further comprisingencoding scalability structure information into in a video parameter setto indicate a maximum difference of the first value of the picture ordercount and the second value of the picture order count.
 6. The method ofclaim 1, further comprising: encoding a temporal identifier value foreach picture, slice, or tile, the temporal identifier value indicating atemporal sub-layer, wherein each coded picture, coded slice, or codedtile in a same access unit has a same temporal identifier value; andencoding a spatial layer identifier value for each picture, slice, ortile, the spatial layer identifier value indicating a spatial layer. 7.The method of claim 1, further comprising: encoding scalabilitystructure information to one of a slice header, a group of blocks (GOB)header, a tile header, and a tile group header.
 8. The method of claim1, further comprising: encoding scalability structure to one of apicture parameter set, a header parameter set, a tile parameter set, andan adaptation parameter set.
 9. The method of claim 1, furthercomprising: encoding reference information to one of a slice header, agroup of blocks (GOB) header, a tile header, and a tile group header;encoding, to a location indicated in the reference information, ascalability structure corresponding to one of a picture parameter set, aheader parameter set, a tile parameter set, and an adaptation parameterset.
 10. A device for video encoding comprising: at least one memoryconfigured to store program code; and at least one processor configuredto read the program code and operate as instructed by the program code,the program code including: first encoding code configured to cause theat least one processor to encode, to a coded video sequence, at leastone of a first picture, a first slice, and a first tile with a firstvalue of a picture order count; and second encoding code configured tocause the at least one processor to encode, to the coded video sequence,at least one of a second picture, a second slice, and a second tile witha second value of the picture order count, wherein the at least one ofthe first picture, the first slice, and the first tile belong to a firstaccess unit among access units, and the at least one of the secondpicture, the second slice, and the second tile belong to the firstaccess unit, wherein the first value of the picture order count and thesecond value of the picture order count are different, and wherein thefirst access unit corresponds to a time instance; and third encodingcode configured to cause the at least one processor to encode, to a highlevel syntax structure, a syntax element poc_cycle_au, wherein a valueof the poc_cycle_au corresponds to a number indicating how many pictureorder count values are associated with the first access unit and amaximum difference between the first value of the picture order countand the second value of the picture order count in the first accessunit.
 11. The device of claim 10, further comprising: fourth encodingcode configured to cause the at least one processor to encode, to thehigh level syntax structure, a syntax element of vp_spoc_cycle_au,wherein the value of ps_poc_cycle_au is indicative of all coded picturesor slices in a coded video sequence; and fifth encoding code configuredto cause the at least one processor to encode, to the high level syntaxstructure, a syntax element of slice_poc_cycle_au, wherein the value ofslice_poc_cycle_au is indicative of the poc_cycle_au of a current slice.12. The device of claim 10, further comprising: sixth encoding codeconfigured to cause the at least one processor to encode, to the highlevel syntax structure, based on poc_cycle_au being constant for eachaccess unit in the coded video sequence, a vps_constant_poc_cycle_per_auequaling 1; and seventh encoding code configured to cause the at leastone processor to encode, to the high level syntax structure, based onpoc_cycle_au being variable across access units in the coded videosequence, a vps_constant_poc_cycle_per_au equaling
 0. 13. The device ofclaim 10, further comprising an eighth encoding code configured to causethe at least one processor to encode scalability structure informationinto in a video parameter set to indicate a maximum difference of thefirst value of the picture order count and the second value of thepicture order count.
 14. The device of claim 10, further comprising:ninth encoding code configured to cause the at least one processor toencode a temporal identifier value for each picture, slice, or tile, thetemporal identifier value indicating a temporal sub-layer, wherein eachcoded picture, coded slice, or coded tile in a same access unit has asame temporal identifier value; and tenth encoding code configured tocause the at least one processor to encode a spatial layer identifiervalue for each picture, slice, or tile, the spatial layer identifiervalue indicating a spatial layer.
 15. The device of claim 10, furthercomprising: eleventh encoding code configured to cause the at least oneprocessor to encode scalability structure information to one of a sliceheader, a group of blocks (GOB) header, a tile header, and a tile groupheader.
 16. The device of claim 10, further comprising: twelfth encodingcode configured to cause the at least one processor to encodescalability structure to one of a picture parameter set, a headerparameter set, a tile parameter set, and an adaptation parameter set.17. The device of claim 10, further comprising: thirteenth encoding codeconfigured to cause the at least one processor to encode referenceinformation to one of a slice header, a group of blocks (GOB) header, atile header, and a tile group header; fourteenth encoding codeconfigured to cause the at least one processor to encode, to a locationindicated in the reference information, scalability structure from oneof a picture parameter set, a header parameter set, a tile parameterset, and an adaptation parameter set.
 18. A non-transitory computerreadable medium storing instructions, the instructions comprising: oneor more instructions that, when executed by one or more processors of adevice, cause one or more processors to: encode, to a coded videosequence, at least one of a first picture, a first slice, and a firsttile with a first value of a picture order count; and encode, to thecoded video sequence, at least one of a second picture, a second slice,and a second tile with a second value of the picture order count,wherein the at least one of the first picture, the first slice, and thefirst tile belong to a first access unit among access units, and the atleast one of the second picture, the second slice, and the second tilebelong to the first access unit, wherein the first value of the pictureorder count and the second value of the picture order count aredifferent, and wherein the first access unit corresponds to a timeinstance; and encode, to a high level syntax structure, a syntax elementpoc_cycle_au, wherein a value of the poc_cycle_au corresponds to anumber indicating how many picture order count values are associatedwith the first access unit and a maximum difference between the firstvalue of the picture order count and the second value of the pictureorder count in the first access unit.